This project has as its goal the characterization of herpes simplex virus type 1 transcription and its control. The general approach is to establish a cell-free transcription system capable of producing RNA molecules similar to those produced during the course of normal infection. Our progress to date involves the preparation and characterization of the viral DNA and RNA polymerase components of the cell-free system. The density (1.726 g/cc) and the molecular weight (approximately 96 x 10 to the 6th power d.) of the purified viral DNA correspond to values cited in the literature. The DNA is terminally redundant as shown by the formation of circles after partial digestion with lambda exonuclease followed by annealing. Under conditions for RNA-DNA hybridization in solution, total RNA obtained from cells labeled with H3-uridine 3-7 hours postinfection hybridizes with purified HSV-1 DNA to the level of 2.2 percent. The transcription of HSV-1 in nuclei isolated from infected cells is blocked by the toxin alpha-amanitin, suggesting that the nucleoplasmic form of the human cell RNA polymerase is responsible for viral transcription during infection. KB cell nuclear polymerases (two species) have been partially purified and characterized in terms of optimal conditions for transcription and sensitivity to alpha-amanitin. Both species can transcribe HSV-1 DNA in vitro.